Method and device for changing a semiconductor wafer position

ABSTRACT

A mechanical apparatus and method are disclosed for orienting and positioning semiconductor wafers while avoiding contamination of elements on the faces thereof, by only contacting the peripheries thereof. The apparatus may include a frame for wafer supports and a semiconductor wafer gripping arm. The gripping arm is mounted on a translator for movement in X, Y, and Z directions to engage and move wafers in, from, and between supports. The gripping arm comprises a, rigid structure with a plurality of semiconductor support wheels mounted thereon to support a wafer only around its periphery. A drive wheel is provided to orient a supported wafer rotationally while it is being supported around its periphery. A detector is provided to detect orientation of the wafer relative to a notch or other position mark on its periphery.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns those fields involving the manufacture ofelectronic components, primarily the fabrication of integrated circuitsfrom substrates or semiconductor wafer materials, such as silicon, moreparticularly the mechanical procedures and devices used to change theposition of at least one semiconductor wafer provided with at least onepositioning mark and placed in a support intended to hold a plurality ofsemiconductor wafers.

2. Discussion of Related Art

The prior art teaches that such methods consist primarily in grasping asemiconductor wafer by one of its faces to change its position,primarily by displacing it from one location to another, whereby devicesused to implement these methods comprise means allowing a wafer to begrasped by suction in the central region of one of its faces.Independently of the displacement of the wafers from one location toanother, the semiconductor wafers are oriented in such a way that theirpositioning mark is placed in a predetermined position, which operationmay consist, for example, in aligning the positioning marks on all thewafers intended to be moved or situated in a common support.

The disadvantage of the methods and devices of the prior art is thatthey can lead to contamination of the semiconductor wafers resultingfrom the grasping of said wafers by one of their faces, which consistsof a material that is highly sensitive to various forms ofcontamination, the risk of contamination being further enhanced by thefact that there is contact between the face and an object. Moreover, themethods and devices according to the prior art require considerable timefor the operations of displacement and orientation of one or severalsemiconductor wafers, these operations being managed independently,which results in longer processing periods for semiconductor wafers andtherefore higher processing costs.

We are familiar with document U.S. Pat. No. 5,102,291, which refers to amethod and apparatus for orienting a silicon wafer located in a supportby grasping its periphery so as to minimize possible contamination fromdirect contact with its faces. Wafers are grasped one by one between twogripper arms movable in translation with respect to one another along astraight line, which are urged toward each other in translation alongthe guide direction until the two arms exert pressure against theperiphery of the wafer being grasped by means of four pressure wheelsthat lift the wafer prior to contact of the wheels against the peripheryof the wafer, the grasped silicon wafer being capable of beingrotationally oriented to a specific position with respect to the supportby means of pressure wheels rotating in the plane of the wafer, at leastone of which is motorized. Moreover, the apparatus is used to move thegrasped wafer in a straight line only because of the two gripper arms.Detection of the desired orientation of the wafer can take place bymeans of a mechanical, optical, electrical, or other type of sensor. Forwafers provided with a notch, the document specifies a pin that issmaller than the notch and which penetrates the notch when the wafer isin a desired position.

We are also familiar with U.S. Pat. No. 5,445,486, which relates to anapparatus for transferring silicon wafers from one support to another bymeans of a gripper arm inserted between wafers in a support, the gripperarm grasping one or more wafers by the periphery of their bottomsurface. The apparatus does not have a means for orienting thetransferred wafers.

The intended processing of semiconductor wafers can include any processinvolving a change in position of a wafer, of several wafers, or of allthe semiconductor wafers located in a common support, as, for example,the transfer of wafers from one support to another, the alignment ofmarks for the purpose of identifying wafers in the support, or evenmodification of the angular position of the semiconductor wafer found inthe support for the placement of marks at a predetermined position.

The present invention proposes to overcome the above disadvantages andprovide other advantages. One object of the present invention is toenable the change of position of at least one semiconductor wafer whileavoiding any contamination resulting from grasping the wafer by one ofits faces and, furthermore, reducing the risks of contamination.

Another object of the present invention is to enable a change ofposition of at least one semiconductor wafer, thus modifying theorientation of a wafer while another processing operation is takingplace, especially the displacement or transfer of the wafer.

Another object of the present invention is to provide increased spacewithin a semiconductor wafer processing station by eliminating the needfor specific equipment for the orientation or alignment of positioningmarks on wafers.

Another object of the present invention is to enable a plurality ofsemiconductor wafers to be grasped and oriented, the orientation of thewafers occurring simultaneously and, moreover, simultaneously withanother operation, such as the displacement of a plurality of wafers.

SUMMARY OF THE INVENTION

More specifically the invention consists in a mechanical method forchanging the position of at least one semiconductor wafer provided withat least one positioning mark and placed in a support intended to housea plurality of semiconductor wafers, characterized in that it comprisesthe following steps:

penetration of said support by means of a gripper arm with a firstmovement of said arm according to a first direction in space

seizure of said at least one semiconductor wafer by the periphery ofsaid wafer with a second movement of said arm according to a seconddirection in space

orientation of said at least one semiconductor wafer, grasped in such away that said positioning mark is placed in a predetermined position.

Seizure of the semiconductor wafer by its periphery helps reducecontamination of the wafer and helps avoid contamination resulting fromgrasping a face of the semiconductor wafer, while orientation of thewafer when grasped enables this operation to take place simultaneouslywith other operations, such as displacement of the wafer. The operationof orienting a wafer when it is being seized helps avoid the use of aspecific processing station for orienting the semiconductor wafers,resulting in increased space for processing the wafers.

According to an advantageous characteristic of the invention, the methodaccording to the invention also comprises the following steps:

withdrawal of said at least one semiconductor wafer from said supportwith a third movement of said gripper arm along said first direction,opposite said first movement

displacement of said at least one semiconductor wafer from one locationto another in a three-directional or -dimensional space, with movementsof said arm being chosen from among the three directions in space, saidstep consisting of

orienting said at least one semiconductor wafer in such a way as toplace said positioning mark in a predetermined position, simultaneouslywith movements of said gripper arm.

According to an advantageous characteristic, the method according to theinvention consists in:

penetration by means of a gripper arm of said support with a firstmovement of said arm along a first direction in space

seizure of a plurality of semiconductor wafers by their periphery with asecond movement of said arm along a second direction in space

orientation of said semiconductor wafers in such a way as to align saidrespective positioning marks of said semiconductor wafers.

According to an advantageous characteristic, the above method alsocomprises the following steps:

withdrawal of said plurality of semiconductor wafers from said supportwith a third displacement of said gripper arm along said firstdirection, opposite said first displacement

displacement of said plurality of semiconductor wafers from one locationto another in a three-directional or -dimensional space, withdisplacements of said arm chosen from among the three directions ofspace, said step consisting in the orientation of said graspedsemiconductor wafers in such a way as to align their respectivepositioning marks and taking place simultaneously with displacements ofsaid gripper arm.

The invention also concerns a device for changing the position of atleast one semiconductor wafer provided with at least one positioningmark and placed in a support intended to house a plurality ofsemiconductor wafers, said device comprising a gripper arm of said atleast one semiconductor wafer, means for displacing said gripper arm,said gripper arm comprising:

means for gripping said at least one semiconductor wafer by itsperiphery

means for orienting said at least one semiconductor wafer, saidorienting means cooperating with said grasping means to place saidpositioning mark in a predetermined position said grasping means andsaid orientation means being arranged on a rigid structure, saidgrasping means being distributed along the perimeter of the periphery ofsaid at least one semiconductor wafer, and in that said displacementmeans of said gripper arm comprises means for displacement along threedirections in space.

According to an advantageous characteristic, said gripping meanscomprise:

means for grasping the periphery of a plurality of semiconductor wafers

means for orienting said semiconductor wafers, said orienting meanscooperating with said means of grasping so as to align said respectivepositioning marks of said semiconductor wafers.

The invention also concerns a semiconductor wafer gripper arm providedwith at least one positioning mark, to realize the seizure of at leastone semiconductor wafer placed in a support intended to house aplurality of semiconductor wafers, characterized in that said armcomprises:

means for grasping the periphery of said at least one semiconductorwafer

means for orienting said at least one semiconductor wafer, saidorienting means cooperating with said grasping means so as to place saidpositioning mark in a predetermined position

said grasping means and said orientation means being arranged on a rigidstructure, said grasping means being distributed over the perimeter ofthe periphery of said at least one semiconductor wafer.

According to an advantageous characteristic, said grasping meanscomprise at least three stops provided respectively with a degree offreedom in rotation and distributed along the perimeter of the peripheryof said at least one semiconductor wafer, and said means of orientationcomprise a friction-operated drive roller for said at least onesemiconductor wafer.

According to another advantageous characteristic, said drive rollerconsists of one of said three stops that is at least partially a drivingelement.

According to another advantageous characteristic, said positioning markis a notch placed along the periphery of said at least one semiconductorwafer, and said three stops comprise respectively two freely rotatingadjacent driven rollers.

According to another advantageous characteristic, said driven rollershave respectively at least one first frustoconical contact surface toprovide support for said at least one semiconductor wafer by means of aperipheral edge on said wafer.

According to another advantageous characteristic, a generatrix of saidat least first frustoconical contact surface forms an angle of between5° and 45° with a perpendicular to said at least one semiconductorwafer.

According to another advantageous characteristic, said driven rollershave, respectively, a second frustoconical surface whose apex isconnected to the base of said first frustoconical surface and whosegeneratrix forms an angle with a perpendicular to said at least onesemiconductor wafer, greater than the angle of the generatrix of saidfirst frustoconical surface.

According to another advantageous characteristic, said means oforientation comprise a first beam capable of being cut whenever saidnotch is not opposite said first beam, and a detector for detecting whensaid first beam has been cut.

ding to another advantageous characteristic, the gripper arm accordingto the invention comprises means for locating the position of said atleast one semiconductor wafer when it is placed in said support.

According to another advantageous characteristic, said locator meanscomprise a second beam cooperating with said first beam and a dimensioncharacteristic of said at least one semiconductor wafer to assist inestablishing the position of said at least one semiconductor wafer insaid support.

According to another advantageous characteristic, said locator meanscomprise a third beam cooperating with said first or second beams and adimension characteristic of said at least one semiconductor wafer toassist in establishing the position of said at least one semiconductorwafer in said support when said first or second beam is placed oppositesaid notch.

According to another advantageous characteristic, the gripper armaccording to the invention comprises:

means for grasping a plurality of semiconductor wafers by the periphery

means for orienting said grasped semiconductor wafers, said orientingmeans cooperating with said grasping means to align said respectivepositioning marks of said semiconductor wafers.

BRIEF DESCRIPTION OF THE DRAWINGS

A clearer idea of the invention will be obtained and othercharacteristics and advantages will appear after reading the descriptionthat follows the examples of various embodiments of the methods,devices, and gripper arm according to the invention, together with theattached drawings, which examples are given purely for illustrativepurposes and without in any way limiting the scope of the invention.

FIG. 1 A is a perspective drawing of an example of an embodiment of adevice according to the invention used to change the position of atleast one semiconductor wafer.

FIG. 1B is a perspective drawing of an enlarged detail of FIG. 1A.

FIG. 2 is a perspective drawing of a first example of an embodiment of agripper arm according to the invention.

FIG. 3 is a top view of the example shown in FIG. 2.

FIG. 4 is a side view of the example shown in FIG. 2.

FIG. 5 is a first enlarged detail, providing a side view of the exampleshown in FIG. 2.

FIG. 6 is a second enlarged detail, providing a partial cutaway of theexample shown in FIG. 2.

FIG. 7 is a perspective drawing of a second example of an embodiment ofa gripper arm according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Device 100, shown in FIGS. 1A and partially in 1B, used to change theposition of semiconductor wafers equipped respectively with apositioning mark and placed in a support (not shown) intended to house aplurality of semiconductor wafers, comprises semiconductor wafergripping means 110, means 120 for moving gripping means 110. Grippingmeans 110 will be explained in detail below with the help of FIGS. 2 to6 and comprise means 5 for grasping the semiconductor wafer by itsperiphery, means 6 for orienting the semiconductor wafer in cooperationwith grasping means 5 so as to place the positioning mark in apredetermined position.

Device 100 comprises a framework 101 on which are affixed two supportsfor semiconductor wafers (not shown). The two supports are affixedrespectively to attachment plates (not shown), placed, for example, oneach side of one another and in line with doors 102 and 103, and havingwafers placed horizontally on top of one another in respectivecompartments in the support. Device 100 can be used to transfersemiconductor wafers from one support to another while enabling theplacement of the respective marks on these wafers in a predeterminedposition. To this end gripping means 110 are connected to displacementmeans 120 in such a way that they are mobile in three dimensions X, Y,and Z of space, as shown in FIGS. 1A and partially in 1B.

Gripping means 110, placed opposite a first support attached, forexample, in line with door 103, are used to select the semiconductorwafer to be grasped in this support, by means of a displacement alongthe Z axis, to penetrate the support through displacement along the Yaxis, to grasp the wafer through upward displacement along the Z axiswithout striking a wafer possibly situated above, to withdraw the waferfrom the support by means of an opposite displacement along Y, to usethe displacements in X and Z to position gripper means 110 opposite thesecond support placed in line with door 102 and the appropriatereceptacle in this support for the grasped wafer.

During these displacements, the semiconductor wafer will beadvantageously oriented to a predetermined position, for example, sothat all the semiconductor wafers have their respective marks aligned.Note that, depending on the need, the device shown in FIG. 1A can beused to orient wafers in a support without transferring them to anothersupport. To do so we place gripper means 110 in position to grasp awafer in its support, that is, place means 110 beneath the wafer to begrasped, grasp the wafer by means of an upward displacement along Zwithout striking a wafer possibly situated above, and orient the waferin the chosen position before again placing it in the same receptacle,then withdraw gripper means 110.

FIG. 1B illustrates gripper means 110 connected to a first part 121 ofdisplacement means 120 in such a way as to enable displacement of thegripper means with a degree of freedom in translation along axis Z. Thisfirst part 121 of the displacement means is connected through a degreeof freedom in translation along the Y axis to a second part 122 ofdisplacement means 120, itself connected through a degree of freedom intranslation along the Y axis to framework 101 of device 100, as shown inFIG. 1A.

According to an alternative not shown, gripper means can comprise meansfor grasping a plurality of semiconductor wafers by their periphery andmeans for orienting the grasped semiconductor wafers in cooperation withgrasping means to align the respective positioning marks of saidsemiconductor wafers. This alternative can be obtained by replacing, indevice 100 shown, gripper means 110 by the gripper arm shown in FIG. 7and described below.

It should be noted that gripper arm 1 shown in FIGS. 2 to 4 constitutesgripper means 110 of device 100 shown in FIGS. 1A and partially in 1B.

Gripper arm 1 shown in FIGS. 2 to 4 is used to grasp disc-shapedsemiconductor wafer 2, placed in a support (not shown) intended to housea plurality of similar semiconductor wafers. Semiconductor wafers 2 areprovided respectively with positioning mark 3, essentially having theshape of notch 3, formed on periphery 4 of wafer 2. By periphery 4 ofsemiconductor wafer 2 we refer to the surface formed by the wafersection, including the two terminating edges of this surface. Thissurface formed by the section can, for example, be cylindrical orappreciably assume the shape of an exterior circular half-torus.Alternatively, the periphery of the wafer can comprise the upper andlower annular surfaces of the extremities of the wafer, having the shapeof a thin crown.

Gripper arm 1, shown in FIGS. 2 to 4, comprises means 5 for grasping theperiphery of semiconductor wafer 2, means 6 for orienting thesemiconductor wafer 2 in cooperation with grasping means 5 to placepositioning mark 3 in a predetermined position, as explained below.

Grasping means 5 and orientation means 6 are arranged on rigid structure7, enabling its at least partial insertion between two successive wafersplaced in a support, for example, as shown in FIG. 4 between wafers 2and 2B, and represented by a dashed line. Upper wafer 2A, shown with adashed line, represents a semiconductor wafer placed in the support (notshown) that is not struck when wafer 2 is grasped. Grasping meansadvantageously comprise three stops 8 provided respectively with adegree of freedom in rotation and distributed about the perimeter of theperiphery 4 of wafer 2 and means of orientation 6 comprising a wafer 2friction drive roller 9.

Rigid structure 7 can, for example, assume the shape of a U profile, atthe base of which are located two stops 8, the third stop 8 beingarranged on one 10 of the arms of the U, and drive roller 9, beingarranged on the other 1I arm of the U, as shown in FIG. 3. A support bar12 can connect the branches of the U at midheight, as shown in FIG. 3.The shape of rigid structure 7 can vary extensively and the structurecan be partly inserted between two successive wafers in such a way thatgrasping means 5 can grasp a wafer by its periphery. The rigid structurecan also enable orientation of the grasped wafer without excessivedeformation of the thin part of its extremity before being insertedbetween two wafers. To obtain an efficient gripper arm, we choose astructure 7 providing excellent strength with minimal weight. Arms 10and 11 of the U, which are intended to be able to penetrate between twosuccessive wafers, can advantageously consist of a metal material, andparts 12 and 13 joining the arms, as well as extremities 14 and 15 ofthe arms of the U not penetrating between the semiconductor wafers, canconsist of a rigid plastic material.

Friction drive roller 9 has a friction drive band capable of acting onthe periphery of semiconductor wafer 2 to drive the latter by angulardisplacement, preferably through adhesion to at least part or all of ageneratrix of the surface forming the periphery 4 of wafer 2, to obtaina good coefficient of friction. Drive band 27 on roller 9 can berealized, for example, by means of an O-ring 25 made of an elasticmaterial, preferably hard, for example, one with a Shore hardness ratingof 70 to 80, mounted on drive wheel 26, as shown in FIG. 6. O-ring 25will preferably be machined to have a cylindrical drive surface.

Drive roller 9 is rotationally driven by motor 20 placed on a rigid partof the arm, for example, on support bar 12, as shown in FIGS. 2 to 4.The transmission of rotational movement between motor 20 and roller 9can occur through use of a drive belt, gear mechanism, or somethingsimilar.

The drive roller can, alternatively, consist of one of the three stops8, which would then serve as a drive mechanism, at least partially. Inthis case (not shown) the drive stop would supply angular displacementto the semiconductor wafer, rotational in the case shown, and alsoassist, in cooperation with the two other stops, in grasping thesemiconductor wafer and ensuring the static equilibrium of said wafer.Stop 8 as a drive mechanism would have an appropriate drive band, forexample, as described above for drive roller 9.

The three stops 8 advantageously and respectively comprise two drivenrollers 8A and 813, adjacent and rotationally free, as shown in FIG. 3.This is done to prevent notch 3, constituting the positioning mark ofwafer 2, from interfering with the driving force of the drive roller orthe static equilibrium of the wafer when notch 3 is near stop 8 duringrotation of the wafer or when the notch is located opposite stop 8 whenthe wafer is grasped in the support (not shown). The drive rollers arepositioned in such a way that their respective contact surfaces withwafer 2 are tangent to the surface of the wafer section. Thus, if notch3 falls opposite one of three stops 8A or 813, the adjacent stop, 8B or8A respectively, will supply static and dynamic equilibrium for thewafer. In the situation described above whereby one of stops 8 serves asa driving force, a single roller 8A or 8B would become the driver, theother would be driven.

In the example shown the axes of rotation of driven rollers 8A and 8Band drive roller 9 are perpendicular to the horizontal plane defined bysemiconductor wafer 2. We can easily envisage axes having anotherdirection, based on the contact profile of the rollers on the wafer, insuch a way that said rollers do not come into contact with either faceof the semiconductor wafer.

Driven roller 8A or 8B, as shown in FIG. 5, advantageously has a firstfrustoconical contact surface 16 to enable contact of semiconductorwafer 2 by means of peripheral edge 17 of said wafer. In FIG. 5 roller8A or 8B is shown in side view and is designed to grasp a wafer placedappreciably or exactly horizontally. Advantageously, a generatrix offirst 16 frustoconical contact surface forms an angle a of between 5°and 45° with a perpendicular to semiconductor wafer 2. Advantageously, adriven roller 8A or 8B has a second 18 frustoconical surface whose apex19 is connected to the base of the first 16 frustoconical surface andwhose generatrix forms an angle with a perpendicular to semiconductorwafer 2 that is greater than angle a of the generatrix of the first 16frustoconical surface. Alternatively, apex 19 of second frustoconicalsurface 18 of each stop 8A, 8B may present a horizontal annular planesurface (not shown) having the shape of a crown of minimal radialthickness, enabling the wafer to rest on the annular extremity of itslower surface.

It should be noted that other types of surface of revolution could beemployed to replace frustoconical surfaces 16 and 18, described, forexample, by the first and second surfaces of revolution formed by acurvilinear generatrix resulting in concave, convex, or other surfaces,for example.

The height of first 16 frustoconical contact surface will be defined inaccordance with the available height between two successive wafers, theinclination based on angle a of the generatrix of surface 16, and theprecision of the relative position of the gripper arm with respect to awafer before it is grasped, so that the grasped wafer rests preferablyagainst one of the first 16 frustoconical surfaces or the first andsecond 18 frustoconical surfaces of driven rollers 8A and 8B. Forexample, for a given height of first 16 frustoconical surface, based onthe available space between two successive wafers in the wafer support,the length of the horizontal projection of the generatrix of the firstfrustoconical surface must be greater or equal to the possible radialpositioning error of the arm with respect to the semiconductor wafer.

Driven rollers 8A and 8B are preferably realized using a rigid plasticmaterial and will have low rotational inertia so they can easily bedriven in rotation through friction by the semiconductor wafer. Rollers8A and 8B shall, therefore, preferably be mounted on structure 7 bymeans of bearings (not shown).

It should be noted that driven rollers 8A and 8B, shown in FIGS. 2 to 5,are provided to enable seizure of a wafer arranged horizontally, asdescribed above. However, ways of grasping wafers placed in anotherposition, vertical for example, can also be envisaged. In this case therollers should have means for preventing the wafer from freeing itselffrom the grasping means under the effect of gravity or movement of thegripper arm, such as, for example, a third frustoconical surface (notshown) symmetric with the second frustoconical surface with respect tothe plane of the wafer, one of three stops 8 being then, for example,movably mounted on rigid structure 7 to enable the wafer to free itselfof the third frustoconical surface and the movable stop to come intocontact with the wafer section so said wafer has only one degree offreedom in rotation.

Means of orientation 6 of the gripper arm shown in FIGS. 2 to 4advantageously comprise a first beam 21 capable of being cut whenevernotch 3 of wafer 2 is not opposite beam 21, and cutoff detector 23 offirst beam 21. Beam 21 can, for example, be a preferably vertical beamof light emitted by light-emitting diode 22 and the detector 23 aphotosensitive cell placed opposite the light-emitting diode. Beam 21can be placed in such a way that, during angular displacement of wafer 2from the effect of drive roller 9, beam 21 can traverse notch 3 until itstrikes photosensitive cell, beam 21 being in the opposite case cut bywafer 2. When the position of notch 3 has been identified by receptionof beam 21 on photosensitive cell, wafer 2 is oriented by drive roller 9with the desired angular value to place mark 3 in a predeterminedposition. Operation of roller 9 and photosensitive cell will at least beadvantageously operated and controlled by a central unit (not shown)advantageously automated as a function of the operations to be carriedout.

The gripper arm shown in FIGS. 2 to 4 advantageously comprises means 21,24 for identifying the position of semiconductor wafer 2 when it isplaced in a support (not shown). The locator means provide optimalpositioning of the gripper arm before seizure of semiconductor wafer 2.Identification consists in locating any two points on the periphery 4 ofwafer 2 as it is grasped, for example, by means of the two beams 21 and24 placed on structure 7 of the arm, and respectively describing the twopoints in a horizontal plane, as shown in FIG. 3 in the plane of thedrawing. Beam 24 can, for example, be a light beam emitted by alight-emitting diode and the detector a photosensitive cell placedopposite the emitting diode. Locator means advantageously comprise first21 beam and second 24 vertical beam cooperating with the first beam anda characteristic dimension of semiconductor wafer 2, in the example theoutside diameter of the wafer, to establish the position, within ahorizontal plane, of the semiconductor wafer in the support (not shown).

The two points on the periphery of wafer 2 are located through smallapproaching movements of the arm containing beams 21 and 24 so it ispositioned suitably for grasping the wafer. The two distinct beams 21and 24 are used to locate the chord of an arc on the circular peripheryof wafer 2 once the beams are cut by the periphery of the wafer, whichsaid chord, combined with knowledge of the diameter of this circularpart of the wafer, can be used to determine the position of the waferand place the arm in an appropriate relative position for grasping thewafer between stops 8, as explained above.

It should be noted that beam 21, used as means for orienting the wafer,is also advantageously used as a locating means to simplify the gripperarm. It is of course possible alternatively to use the two distinctbeams as means of orientation and location respectively.

Alternatively and advantageously, locating means comprise a third beam(not shown) cooperating with the first 21 or second 24 beam and adimension characteristic of the semiconductor wafer, its outsidediameter in the example, to enable us to establish the position of thesemiconductor wafer in its support when the first or second beam isplaced opposite the notch used as a positioning marker. To this end thethird beam is placed in any position that can be used to obtain thechord of an arc on the periphery of the wafer, in combination with thatof the first or second beam, which is not placed opposite the notch, anddetermine the configuration of two points of a chord of an arc on theperiphery of the wafer. In effect the notch generally penetrates thewafer by a non-negligible length and could consequently result inincorrect measurement of the arc and thus of the position of the wafer.The third beam is used to ensure that at least two beams will not beopposite the notch when obtaining a chord. The third beam can berealized similarly to the two first.

The gripper arm shown in FIGS. 2 to 4 operates as follows: The arm isintroduced into a support containing semiconductor wafers whose positionwe wish to modify, for example, as described above with the help ofFIGS. 1A and 1B. The approach of the arm toward the wafer is realized bylocating means, also as described above, in such a way that the arm isplaced in a position such that its upward movement results in seizure ofthe wafer between rollers 8A and 8B of the arm. During seizure, thewafer must rest on at least the first frustoconical surfaces 16 of apart of rollers 8A, 8B in such a way that said wafer centers itself bygravity or, once set in angular movement by the drive roller,appreciably or exactly at the apex 19 of the second frustoconicalsurface 18 of each driven roller. Thus the wafer preferably rests onstops 8A and 8B by its lower peripheral edge 17, as shown in FIG. 5.Angular movement of the wafer is then initiated by drive roller 9 untilnotch 3 passes through beam 21 enabling photosensitive cell to beactivated, thus enabling us to identify the angular position of thewafer, whose rotation is then realized with respect to this position soas to place the wafer in the position so determined. During rotation ofthe wafer, it rests on the first frustoconical surfaces 16 of a part ofrollers 8A, 8B. When the desired position is reached, the wafer isresting in the support as described above.

The gripper arm shown in FIG. 7 comprises means for grasping theperiphery of a plurality of semiconductor wafers 2, means for orientingthe grasped semiconductor wafers, cooperating with grasping means so asto align the respective positioning marks of the semiconductor wafersgrasped by the arm. Grasping means comprise a plurality of partialstructures 7 capable of being respectively inserted in the free spacesbetween semiconductor wafers in a support (not shown) and connected bycommon rigid support 30 as shown. Each structure bears a drive rollerrotating against the wafer it is intended to support, three supportstops 8 for this wafer, and two beams 21 and 24, as described above forstructure 7. The arm shown in FIG. 7 can be advantageously used tosimultaneously grasp a plurality of wafers 2 placed in a support andadvantageously simultaneously orient these wafers in such a way thatthey are placed in a predetermined position, for example, so as to aligntheir notches 3. Thus alignment of the notches can take place, forexample, during transfer of the wafers from one location to another.

Several examples of the methods according to the invention will now bedescribed. A first example of the method according to the inventionconsists of a mechanical method enabling us to change the position ofone or more semiconductor wafers provided with a notch and placed in asupport intended to house a plurality of semiconductor wafers, whichconsists of grasping the semiconductor wafer or wafers by theirperiphery and orienting the semiconductor wafer or wafers so as to placeits (their) notch(es) in a predetermined position. Such a method can,for example, be implemented with a device according to the invention asdescribed above, which enables us to align notches on semiconductorwafers placed in a support without removing those wafers from theirsupport.

A second example of the method according to the invention consists inmoving the semiconductor wafer or wafers from one location to anotherand simultaneously orienting these wafers so as to place their notchesin a predetermined position, for example, by aligning the notches. Sucha method can be implemented using a wafer transfer device as describedabove.

What is claimed is:
 1. A process for changing the position of asemiconductor wafer having a positioning guide and supported in ahousing, comprising: moving a gripping arm in a first directionsubstantially parallel to the plane of said semiconductor wafer topenetrate into said housing; moving said gripping arm within saidhousing in a second direction substantially perpendicular to said firstdirection to support said semiconductor wafer, said gripping at-rnsupporting said semiconductor wafer only at a plurality of locationsalong the periphery thereof; and rotating said semiconductor wafer whilesupported by said gripping arm to place said positioning guide in aselected position.
 2. The process of claim 1, further comprising: movingsaid gripping arm in a third direction opposite said first direction toremove said semiconductor wafer from said housing.
 3. The process ofclaim 2, further comprising: moving said gripping arm in selecteddirections to move said wafer to a selected location; and rotating saidsemiconductor wafer simultaneously with movement of said gripping arm.4. The process of claim 2, further comprising: moving said gripping armin a fourth direction substantially perpendicular to said first, secondand third directions to move said semiconductor wafer to a selectedlocation outside said housing.
 5. The process of claim 4 wherein saidselected location is within another housing.
 6. The process of claim 3further comprising rotating and moving a plurality of semiconductorwafers simultaneously.
 7. The process of claim 6 further comprisingrotating and moving a plurality of semiconductor wafers in a pluralityof housings simultaneously.
 8. An apparatus for changing the position ofa semiconductor wafer having a positioning guide and supported in ahousing, comprising: a gripping arm; a translator adapted to support andmove said gripping arm in three dimensions to permit movement of saidgripping arm into and out of said housing, into and out of supportingengagement with said semiconductor wafer in said housing, and to andfrom locations outside said housing; a plurality of wafer supportscoupled to said gripping arm and arranged to support said semiconductorwafer at locations around its periphery; and a rotatable driver coupledto said gripping arm for engaging the periphery of said semiconductorwafer for rotating said semiconductor wafer while supported by saidgripping arm to place said positioning guide in a selected position. 9.The apparatus of claim 8 wherein said gripping arm is provided with adetector for detecting when said semiconductor wafer is in said selectedposition.
 10. The apparatus of claim 9 wherein said translator isadapted to support said gripping arm and to move said gripping arm insix directions in three dimensions, thereby permitting said gripping armto be moved into and out of said housing in first and second directionsparallel to the plane of said semiconductor wafer, within said housingin third and fourth directions substantially perpendicular to said firstand second directions to engage and disengage said semiconductor waferwithin said housing, and in fifth and sixth directions substantiallyperpendicular to said first, second, third, and fourth directions topermit movement of said semiconductor wafer to said locations outsidesaid housing.
 11. The apparatus of claim 9 wherein said detectorcomprises: a first light beam generator located at a first selectedlocation on said gripping arm relative to the periphery of saidsemiconductor wafer to generate a first light beam at said firstselected location; and a first light beam detector located at said firstselected location on said gripping arm relative to the periphery of saidsemiconductor wafer opposite said first light beam generator fordetecting the presence and absence of said first light beam depending onthe position of said positioning guide relative to said detector. 12.The apparatus of claim 11 further comprising: a wafer guide disposed onsaid gripping arm for detecting the position of said semiconductor waferon said gripping arm.
 13. The apparatus of claim 12 wherein said waferguide comprises: a second light beam generator located at a secondselected position on said gripping arm relative to the periphery of saidsemiconductor wafer, said second light beam generator located apredetermined distance from said first light beam generator forgenerating a second light beam at said second selected position; and asecond light beam detector located at said second selected position onsaid gripping arm relative to the periphery of said semiconductor waferopposite said second light beam generator to detect the presence andabsence of said second light beam indicating the presence and absence ofsaid periphery of said semiconductor wafer on said gripping arm at saidsecond selected position.
 14. The apparatus of claim 13 wherein saidwafer guide comprises: a third light beam generator located at a thirdselected position on said gripping arm relative to the periphery of saidsemiconductor wafer, said third light beam generator located apredetermined distance from said first arid second light beam generatorsfor generating a third light beam at said third selected position; and athird light beam detector located at said third selected positionrelative to the periphery of said semiconductor wafer opposite saidthird light beam generator to detect the presence and absence of saidthird light beam indicating the presence and absence of said peripheryof said semiconductor wafer on said gripping arm at said third selectedposition.
 15. The apparatus of claim 8 wherein said gripping arm isadapted to support, rotate, and move a plurality of semiconductor waferssimultaneously.
 16. The apparatus of claim 8 wherein said rotatabledriver is adapted to rotate said semiconductor wafer simultaneously withsaid translator moving said gripping arm.
 17. The apparatus of claim 8wherein said gripping arm comprises a rigid support structure for saidwafer supports and said rotatable driver.
 18. The apparatus of claim 8including at least three wafer supports, said wafer supports beingsubstantially free to rotate and distributed about the periphery of saidsemiconductor wafer, and said rotatable driver comprising a frictiondriving roller.
 19. The apparatus of claim 8 wherein one of said wafersupports comprises said rotatable driver.
 20. The apparatus of claim 8wherein said positioning guide comprises a notch in the periphery ofsaid semiconductor wafer.
 21. The apparatus of claim 8 wherein saidwater supports comprise rotatable rollers having a first truncated wafercontact surface adapted to engage a peripheral edge of saidsemiconductor wafer.
 22. The apparatus of claim 21 wherein said firsttruncated wafer contact surface forms an angle (α) between approximately5 and 45 degrees with a line perpendicular to the plane of saidsemiconductor wafer.
 23. The apparatus of claim 22 wherein saidrotatable rollers have a second truncated surface adapted to support theperipheral edge of said semiconductor wafer, said second truncatedsurface being sloped relative to the adjacent surface of saidsemiconductor wafer, a peak of said second truncating surface abuttingsaid first truncated surface, and forming an angle with respect to saidline perpendicular to the plane of said semiconductor wafer which islarger than the angle (a) formed between said first truncated surfaceand said line.